1. Technical Field
The present invention relates to a wireless power transmission system that wirelessly charges a battery for driving an electronic device, and a method of controlling the wireless power transmission system, and more particularly, to a wireless power transmission system capable of minimizing damage due to a reflective wave generated when a battery is charged, and a method of controlling the wireless power transmission system.
2. Description of the Related Art
A variety of portable electronic products has been recently launched and distribution thereof has been remarkably increasing along with development of IT technology. Such portable electronic products are used while users are moving, and thus the performance of batteries is important.
Charging devices for charging batteries of portable electronic products with electricity supply power to battery packs using a terminal supply method.
However, in a case where charging devices and batteries are connected to or disconnected from each other, since terminals of charging devices and batteries have different electric potentials, discharging phenomenon may instantly occur in terminals. Further, impurities may be collected in terminals of charging devices and batteries over time, which causes fire or reduction in life and deterioration of performance of charging devices and batteries.
A wireless power transmission system has been proposed to solve the problem of the terminal supply method. In the wireless power transmission system, a transmission device generates electric energy and transmits the electric energy wirelessly, and a reception device receives the electric energy wirelessly and charges a battery with the electric energy. To achieve stability of the battery and efficiency of the wireless power transmission system, the battery is quickly charged with constant current until a charging voltage of the battery reaches a previously set voltage in a constant current (CC) mode, and the battery is charged with low current while maintaining the charging voltage of the battery constant if the charging voltage of the battery reaches the previously set voltage in a constant voltage (CV) mode.
However, the conventional wireless power transmission system has a problem in that the electric energy transmitted by the transmission device is partially received in the reception device and is charged in the battery in a section (a first section) in which the CC mode is changed into the CV mode, and the remaining electric energy acts as a reflective wave and damages the transmission and reception devices.
Furthermore, the above-described problem also takes place in a physical discharging section (a second section) in which the voltage charged in the battery is completely discharged since portable electronic products are not used for a long time or in an initial charging section (a third section) in which the battery is electrically cut-off discharged. In this regard, the first, second, and third sections are united and referred to as an NDR section.